The uptake of radial approach for coronary diagnostic and interventional procedures over the past few years has been nothing short of extraordinary. Once used in <2% of all cases in the United States, transradial procedures grew 8-fold between 2007 and 2012, and show little sign of slowing. Concomitant with the increase in the clinical use of radial access has been a growth in the evidence supporting its role in various angiographic and high-risk scenarios. Studies have also addressed technical aspects of the procedure delineating best practices and tips for radial access, traversing difficult arm vasculature, and radial artery hemostasis. These studies have broadened the application of radial approach, improved the transradial technique, and favorably impacted patient outcomes.

An added positive effect is that by subjecting long held beliefs to the rigor of randomization or robust analysis, certain myths have been proven wrong. In this issue of JACC: Cardiovascular Interventions, van Leeuwen et al. (1) perform an elegant study to disprove the myth that transradial procedures adversely affect upper limb function. Patients undergoing elective percutaneous procedures via either the radial or femoral arterial access had their upper limb function assessed using a validated instrument. Femoral access, of course, would not be expected to affect the upper limb, and thus served as a useful control. There was no significant difference between radial and femoral access with respect to upper limb function, cold intolerance, or other procedure-related extremity complaints. Moreover, the presence of palmar arch flow in the hand used for radial access did not affect any of the outcomes. This study is the latest in a series of studies that have challenged our preconceived notions about the structure and function of the hand vasculature, the role of testing for dual circulation, and alternative arm access for cardiac catheterization.

The advantage of the radial artery as an access site for cardiac catheterization is primarily due to its superficial location, which lends itself to hemostasis. A limitation of radial approach is radial artery occlusion (RAO) and one of the factors that may have stunted the adoption of radial access is the misconception that the risk of RAO is worse than the benefit in bleeding. Indeed, many operators use tests that determine the presence of ulnopalmar arterial arches (so-called “dual circulation”), like the modified Allen or Barbeau tests, to identify patients who are not candidates for transradial procedures. Given that 6% to 10% of patients may have a test result that would be felt to preclude radial arterial access, the routine use of these tests denies a safer procedure to a significant number of patients. Recently, the RADAR (Should Intervention Through Radial Approach be Denied to Patients With Negative Allen's Test Results?) trial has definitively and conclusively shown that tests of ulnopalmar arterial patency have no predictive value with respect to digital ischemia (the most feared complication of RAO), post-procedure ulnar artery flow, or even capillary lactate levels (2). Similar to the study by van Leeuwen et al. (1), there was no difference across the Allen test results when functional outcomes such as handgrip strength were examined.

These findings are not surprising when considering the arterial anatomy of the human arm and hand, which provides extensive superficial and deep collaterals. This complex and elegant arterial circulation also suggests another route for angiography—the ulnar artery. The ulnar artery is the continuation of the brachial artery and was the initial access site used by Zimmerman in 1949 (3) for retrograde catheterization of the left ventricle. It is often larger and has a straighter course compared with the radial artery and rarely has anomalies. A case series from a high-volume center demonstrated the feasibility and safety of utilizing ipsilateral ulnar access even if initial radial artery access fails (4). Patients in this series underwent transulnar catheterization if there was inability to puncture the radial artery, a weak or absent radial pulse, radial artery spasm, an uncrossable radial loop, or a small-caliber radial artery—many situations that commonly would be considered contraindications to ipsilateral ulnar access. Procedural success via the ulnar artery was 97%, with 3% of patients needing crossover to femoral access. The rate of ulnar artery occlusion (UAO) was 3.1% at 30 days, which was asymptomatic. Importantly, there was no UAO among patients with ipsilateral RAO, suggesting an “accommodative” ability of the hand circulation. The SWITCH (same wrist intervention via the cubital [ulnar] artery in case of radial puncture failure for percutaneous cardiac catheterization or intervention) registry, in which an attempt at ipsilateral ulnar access was mandated in case of an inability to place an introducer sheath in the radial artery, bolsters these data (5). Failure to place a radial sheath occurred in 2.5% of patients, and successful ulnar artery access was obtained in 86% of these patients. There were no cases of hand ischemia despite access in both the radial and ulnar arteries.

On the basis of these data, one could consider whether the ulnar artery should be used as primary access instead of the radial artery. There are important anatomic limitations to a primary ulnar approach. The ulnar artery is often situated more deeply and without an underlying bone base compared with the radial artery, and the ulnar nerve runs alongside. This may increase the risk of forearm hematoma and ulnar nerve injury. A direct comparison of radial and ulnar access was performed in the AURA of ARTEMIS (Transulnar or Transradial Instead of Coronary Transfemoral Angiographies Study), which randomized 902 patients at 5 sites (6). The primary endpoint was the 60-day composite of access site crossover, major adverse cardiac events, or major vascular events. The trial was stopped early as a result of inferiority of the ulnar approach, primarily driven by a higher rate of access site crossover even after accounting for operator clustering. No patient with an occluded artery experienced hand ischemia. Therefore, the available evidence supports a primary radial approach, and strongly suggests that the ipsilateral ulnar artery can safely be accessed in case of radial failure, thus obviating femoral access. Importantly, the routine use of radial artery angiography through the access needle or cannula before sheath placement may identify patients in whom the ulnar approach may be preferred (Figure 1). Expertise with transulnar procedures could reduce femoral crossover rates and thus further affect bleeding and vascular complications, particularly in high-risk patients such as those undergoing primary percutaneous coronary intervention for ST-segment elevation myocardial infarction. Adequately powered randomized trials should assess the long-term safety of this strategy.

Percutaneous cardiac procedures begin and end with access site management. For coronary angiography and intervention, radial access has emerged as the dominant approach because of its superior safety. The data supporting radial approach have evolved from examining “hard” clinical outcomes such as bleeding, vascular complications, and major adverse cardiac events, to patient-oriented endpoints such as functional outcomes. It is clear that, from the available evidence radial access not only improves clinical outcomes and reduces costs, but also has no adverse effects on arm or hand function. Given the extensive complex arterial circulation available in the upper extremity and the emerging data on ulnar access, we may be approaching the post-femoral era for coronary angiography and intervention.

Footnotes

↵∗ Editorials published in JACC: Cardiovascular Interventions reflect the views of the authors and do not necessarily represent the views of JACC: Cardiovascular Interventions or the American College of Cardiology.

Dr. Rao has been a consultant for Terumo Interventional Systems. Dr. Kedev has reported that he has no relationships relevant to the contents of this paper to disclose.